Persistent Mobile and Toxic Contaminants in Urban Stormwater: the case of Barcelona Municipality

Challenges posed by rapid urbanization, climate change, and the increased frequency of extreme weather events are forcing cities to adapt a new urban water management. Stormwater harvesting represents a prospective local resource, particularly in densely populated arid regions marked by severe water scarcity. Among these, deployment of stormwater blue-green infrastructure (BGI) is a promising practice to mitigate flood risk, while recharging aquifer and reducing combined sewer overflows. However, it is acknowledged that stormwater, highly impacted by anthropogenic contaminants, is a significant carrier of contamination.

Despite legacy and (un)regulated contaminants (e.g., pesticides, drugs, anti-corrosion agents, plasticizers) have already been detected in various water sources, there is still a lack of scientific knowledge on the source, transport and fate of new chemicals of concern (i.e., absence of comprehensive monitoring) in the urban water cycle. For instance, blue-green infrastructure may not ineffectively remove persistent, mobile, and toxic (PMT) organic compounds, allowing them to potentially enter ground and surface waters.

Herein, “first flushes” of urban stormwater (including rainwater) from nearly 30 sites over 3 districts across the municipality of Barcelona, were collected during the period March to April 2022. Sampling design included conventional and pedestrian streets runoff, and BGI inlet/outlets. The results showed that conventional streets were the most polluted areas. More than 30 targeted urban contaminants were investigated using a LC-MS/MS method, 14 of them included in the UBA PMT list. In this preliminary analysis, we observed that all targets were detected in at least one sample, among them 5 chemicals as benzenesulfonamide, 1,3 diphenylalanine, Di-n-butyl phosphate, tolytriazole and TCPP, resulted to be the more ubiquitous (with frequencies >70%) and showed median concentrations higher than 100 ng L^-1. Moreover, BGI effluents showed lower overall PMT concentrations compared to influent runoff waters, highlighting the removal capacity of these stormwater treatment schemes. Results will eventually undergo thorough analysis to identify PMT sources, occurrence, and fate in a spatiotemporal domain. PMTs substances impacting urban stormwaters must be monitored in order to prevent spread in surface and ground waters and enable safe use for water supply.